AlanG

I'm intending to take the car to a new weighbridge later on today to find out a definitive weight for my car. Primarily this is to allow hopefully more accurate data for the AP-22.

I'm also told that it has the facility to weigh the vehicle at each end (front only, back only) as well as corner weights, which i believe may be useful in setting up suspension.

My question is if i have the corner weights and/or front/rear weights, how do i interperate the data to allow me to set up the car for best handling? What would i go for as far as spring poundages etc?

How would you set the car up?

I know very little about suspension side of things so would appreciate any input folks might have.


Alan

Tim W

iTrader: (1)

ALan, don't know if you'll be able to get corner weights from a weighbridge, but give it a go! Would be interested to learn your results...I plan to get mine weighed at somepoint in the not to distant future to find out how much weight has been shed

AlanG

Hi Tim. Long time no speak. Trust you are keeping well.

I don't know how it's done either.
All i know is it took weeks and weeks to get it in and up and running and what i've been told by the people that use it, is that it's capable of doing these things.

Will find out tonight for sure.

Alan

Tim W

iTrader: (1)

Hi Alan, yep, it's been a while hasn't it Currently in a two week enforced rest, but this has allowed me (oh alright, Pat ) to get Slooby running again for the first time in 7 months

I looked at some corner weight scales good for up to 1400kg, which would have cost about 700 quid (new) for the set of 4...would have been fun to play about with geometry/ride settings on some scales to see what affect they had! But I haven't a clue what a good balance would have been, but then again I might no someone who does...let me go ask

Tim W

iTrader: (1)

Right, spoke to the expert from Barretts (who was responsible for one of the top running group N rally car's in the country), and he said that playing about with corner weights on the Scoob wasn't really worth it as the car is inherantly well balanced.

As long as the front is between 5 and 10mm (depending upon how much you want the car to oversteer) lower than the rear it should be perfect!

Kippax

alan - assuming you have height adjustable suspension, level the car and set the ride height to your preference. going off corner weights for diagonal % the equation is:

((front left + rear right)/total)x 100%. opposite for the other diagonal.

say you get 48% for the first diagonal then the other will read obviously be 52%. adjust one corner height until you get as close to 50% as possible.

stu.

AlanG

Thanks for the advice guys.

Hopefully later tonight i'll have definite figures i can then work on.

Alan

AlanG

Okay guys, here's the figures...

The car with 60litres of fuel on board without driver weighed 1360Kg.

Front weight is 800Kg and rear weight is 560Kg.

Here is the odd bit and looking for comments.

Front N/S weighed 400Kg, front O/S weighed 420Kg. Total obviously is 820Kg which is 20Kg out over the total front weight.

Rear N/S weighed 280Kg, rear O/S weighed 300Kg. Again a discrepancy of 20Kg.

The car was weighed in the centre of the weighbridge for total weight and on each half (front / rear) the car overhanged (is that the right word?) the weighbridge at the centreline of the vehicle i.e. the "B" pillar.

For the corner weights, the car was again positioned centreline of car both front and side to be even.

Can this discrepancy be possible?

If so and the weights can be useful to some degree, how would i use these figures to determine suitable spring rates and setting up of the suspension?


Alan

Kippax

thats pretty close

T-uk

commercial weighbridges are not accurate to the nearest kg, usually 20kg differences.

Kippax

alright alan,

from reading books on the subject it seems the only way to shift weight is to physically move weight from the heaviest corner to the others....but, if you have height adjustable suspension you can work with the diagonal weight distribution percentages to improve the handling. my weights with a lever type corner weight gauge were:

front
880 875

650 750
back

therefore the total is 3155 (not actual total weight, just total weight on each levered corner) and the diagonal percentages are:

fl + rr / total x 100% = 51.7% and obviously the remainder = fr + rl / total x100% = 48.3%

by adjusting one corner height, the percentages can be improved. imagine a square plate with a height adjuster in each corner. it is possible to balance the plate on three legs with the fourth retracted. now wind the fourth leg down so it just touches the ground. although this leg makes contact, it has very little weight on it. this is the worst case that needs to be avoided. the answer is to wind the fourth leg further down or wind the diagonally opposite leg up. dont forget all three other weights change by doing this but my car was adjusted to:

front
857 910

673 715
back

which is still 3155 total but the % are now 49.82% and 50.18%

AFAIK, if you have set the overall ride height as desired before you measured, the diagonal percentages are the only real improvement to be made.

i would mess with the o/s front and re-measure the weight with you in the car.

stu.

Tim W

iTrader: (1)

Alan, sorry m8 haven't a clue how to interpret those figures! Stuart seems to have digested the book though

AlanG

No problem Tim.

With the difference in weight front and rear, no wonder the thing wants to understeer!

Alan

Tim W

iTrader: (1)

It's quite alarming to note how nose heavy the scoob is! But then again, is it...By weighing the front/rear of the from the wheels do you get an acurate pciture on weight distribution over the whole car? for example is most of the front end weight ahead or behind the axle line? It would be nice to think that it's behind the axle line, but if it's forward the effect on understeer would be more pronounced...I think...

Whatever, Pat is going to have a hell of a time with his 6 cylinder

dowser

If you're corner weighting, you should include the drivers weight in the seat too...and decide whether you want best handling with full or empty tank

Richard